<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box{
            width:100px;
            height:100px;
        }
        .first{
            background:blue;
            /*float:left;*/
            position:relative;/*relative,下一个图片的原有的位置不动*/
            left:100px;
        }
        .second{
            background:yellow;
            content:'neirong';
            /*float:right;
*/
        }
        .third{
            background: black;
            /*float:left;*/
           /*clear:left;*/
        }
        .second:after{
            content:'a';
           /* display:block;
            clear:both;*/
        }
    </style>
</head>
<body>
<div class="box first"></div>
<div class="box second"></div>
<div class="box third"></div>
</body>
</html>